EXCHANGE 


A  STUDY  OF  THE  EXCITING  POWER  FOR 

FLUORESCENCE  OF  THE  DIFFERENT 

PARTS  OF  THE  ULTRAVIOLET 

SPECTRUM 


A  THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 
OF  CORNELL  UNIVERSITY  FOR  THE  DEGREE  OF 
DOCTOR  OF  PHILOSOPHY 


BY 

LELAND  JAYNES  BOARDMAN 


Reprinted  from  PHYSIC  A  i  .  S.  S.,  Vol.  XX,  No.  6,  December,  1922. 


A  STUDY  OF  THE  EXCITING  POWER  FOR 

FLUORESCENCE  OF  THE  DIFFERENT 

PARTS  OF  THE  ULTRAVIOLET 

SPECTRUM 


A  THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 

OF  CORNELL  UNIVERSITY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 

LELAND  JAYNES  BOARDMAN 


Reprinted  from  PHYSICAL  REVIEW,  S.  S.,  Vol.  XX,  No.  6,  December,  1922, 


A  STUDY  OF  THE  EXCITING  POWER  FOR  FLUORESCENCE 

OF  THE   DIFFERENT   PARTS  OF  THE 

ULTRAVIOLET  SPECTRUM. 


507754 


[Reprinted  from  THE  PHYSICAL  REVIEW,  S.S.,  Vol.  XX.,  No.  6,  December,  1922. 


A  STUDY  OF  THE  EXCITING  POWER  FOR  FLUORESCENCE 

OF  THE  DIFFERENT  PARTS  OF  THE 

ULTRAVIOLET  SPECTRUM. 

BY  LELAND  JAYNES  BOARDMAN. 
SYNOPSIS. 

Intensity  of  Fluorescence  as  a  Function  of  Wave-length  of  Exciting  Light,  0.55  to 
0.2  fj.. — The  purpose  of  the  experiment  was  to  determine  what  wave-lengths  are  effec- 
tive in  excitation  and  what  relations  exist  between  these  wave-lengths  and  the 
corresponding  absorption  and  fluorescence  spectra.  Light  from  a  source  giving  a 
continuous  spectrum  was  dispersed  by  means  of  a  quartz  spectrograph  and  allowed 
to  fall  on  the  substance  to  be  studied  which  was  spread  on  a  flat  surface.  Then 
the  parts  of  the  spectrum  which  excited  fluorescence  were  observed  or  photographed 
by  means  of  the  fluorescent  light.  A  preliminary  study  of  seventy  substances  showed 
that  all  the  oxides  (20)  and  simple  chlorides  (8)  tested  were  not  excited,  a  few 
substances  (7)  including  zinc  silicate,  zinc  sulphate  and  cadmium  phosphate 
fluoresced  faintly,  a  few  responded  well  (anthracene,  eosin,  fluorescein,  phenol- 
phthalein,  calcium  tungstate,  and  phosphorescent  willemite),  while  the  uranyl 
compounds  (20)  fluoresced  strongly.  For  the  last  group  the  effective  spectrum 
extended  from  0.55  to  0.35  M  only,  while  for  the  others  it  extended  continuously 
to  0.2  n  except  in  the  case  of  four  substances  for  which  light  from  0.35  to  0.325  was 
ineffective.  Excitation  band  spectrum  for  twelve  uranyl  compounds  was  determined 
by  measuring  the  density  of  the  plates  as  a  function  of  the  wave-length  by  means 
of  a  sensitive  photoelectric  spectrophotometer.  Some  curves  are  reproduced  and 
the  wave-numbers  corresponding  to  from  35  to  105  maxima  for  each  compound 
are  given.  Comparison  with  absorption  spectra  shows  close  agreement,  an  absorption 
band  corresponding  to  an  excitation  band  in  every  case.  This  relation  had  pre- 
viously been  found  by  Howe  to  hold  for  phosphorescent  sulphides. 

Absorption  Spectrum  of  Twelve  Uranyl  Compounds,  from  0.55  to  0.32  /JL. — Because 
of  the  correspondence  noted  above  the  excitation  bands  may  be  taken  to  be  absorp- 
tion bands  and  thus  the  known  absorption  spectrum  be  considerably  extended  toward 
both  the  red  and  ultraviolet.  Comparison  of  these  bands  with  the  fluorescence 
spectrum  indicates  clearly  many  new  reversing  regions  where  the  fluorescent  light 
obscures  the  absorbing  effect.  These  are  listed. 

INTRODUCTION. 

THE  purpose  of  this  investigation  is  to  study  the  behavior  of  different 
portions  of  the  ultraviolet  spectrum  as  regards  the  ability  of 
exciting  fluorescence.  The  major  part  of  previous  work  in  fluorescence 
has  been  confined  to  a  study  of  the  fluorescence  and  absorption  spectra 
of  various  materials  and  the  relations  between  the  two.  This  enables 
one  to  describe  the  phenomena,  or  state  what  happens  as  the  result  of 
the  mechanism  producing  fluorescence.  It  also  throws  some  light  on 
the  nature  of  the  mechanism  itself. 


VOL.  XX. J  ULTRAVIOLET   SPECTRUM.  553 

It  seemed  probable  that  something  could  also  be  learned  about  this 
mechanism  by  studying  the  means  by  which  it  is  set  in  operation:  in 
other  words  by  studying  the  conditions  and  means  by  which  fluorescence 
is  excited.  As  a  part  of  this  problem  it  is  of  interest  to  determine  what 
wave-lengths  are  effective  in  excitation  and  what  relations  exist  between 
the  excitation,  absorption,  and  the  fluorescence  spectra.  Almost  the 
only  work  that  has  been  done  along  this  line  is  that  of  Stokes,1  and,  for 
a  certain  group  of  materials,  the  work  of  Lenard.2 

The  method  of  the  present  investigation  is  similar  to  that  used  by 
Stokes.  Quartz  was  however  used  in  place  of  glass,  and  better  sources 
of  ultraviolet  light  were  employed. 

Fig.  i  shows  the  arrangement  of  the         s  yy fr/1 

apparatus.  Light  from  the  source 
5  passed  through  a  spectrograph, 
and  then  fell  upon  the  fluorescent 
substance  mounted  in  the  plane  of 
the  plate-holder  of  the  spectro- 
graph at  A . 

With  the  room  darkened  the  fluorescence  was  studied  for  color  and 
relative  intensity  by  the  eye  at  E.  For  more  accurate  study  a  photo- 
graph was  taken  by  means  of  a  camera  lens  L  and  a  plate  at  P.  In  this 
way  the  exciting  power  of  any  region  of  the  ultraviolet  light  was  easily 
determined,  since  the  dispersed  light  fell  immediately  upon  the  specimen 
spread  out  to  intercept  the  entire  beam  of  light. 

It  was  necessary  to  use  a  light  source  which  gives  a  continuous  ultra- 
violet spectrum  as  free  as  possible  from  lines  or  bands.  An  electric 
spark  under  water  was  quite  satisfactory  for  a  large  range  of  the  ultra- 
violet spectrum.  Other  sources  of  light  could  be  used  to  better  advantage 
however  in  the  visible  and  near  ultraviolet  region,  since  it  was  very 
difficult  to  maintain  a  spark  in  water  for  a  sufficiently  long  time  to  give 
a  proper  exposure  for  the  regions  of  weak  fluorescence.  Some  photo- 
graphs were  however  obtained  by  long  excitation  by  the  spark.  By  the 
method  of  producing  the  under-water  spark  used  in  this  work,  which  is 
described  in  another  paper  soon  to  be  published,  it  was  possible  to  main- 
tain a  vigorous  spark  discharge  8  mm.  in  length  for  half  an  hour  in  dis- 
tilled water,  by  means  of  a  Tesla  coil  operated  by  a  transformer  of  one 
kilowatt  capacity. 

It  was  found  that  a  400  c.p.  nitrogen-filled  glass-bulb  Mazda  lamp 
gave  sufficient  intensity  in  the  near  ultraviolet,  and  this  was  used  when 

1  Stokes,  Phil.  Trans.,  p.  463,  1852. 

2  Lenard,  P.     Ueber  Lichtemission  und  deren  Erregung.     Annalen  der  Physik,  31,  p.  641- 
1910. 


554  LELAND   JAYNES  BO  A  RDM  AN.  [§£?S! 

possible  because  of  its  greater  convenience.     For  somewhat  shorter  wave- 
lengths a  similar  lamp  with  a  quartz  bulb  was  used. 

Two  spectrographs  were  used :  the  Fuess  type,  which  gives  a  spectrum 
about  5  cm.  long,  range  580  my.  to  200  m^,  and  a  Hilger  instrument  which 
gives  five  regions  (5  settings)  of  the  spectrum  with  a  total  length  of  about 
30  cm.,  range  800  m\i  to  205  ra/z.  This  spectrograph,  which  proved  to  be 
excellent  for  the  purpose,  is  constructed  so  that  five  adjustments  of  its 
parts  can  be  made  for  each  of  the  five  ranges  or  parts  of  the  spectrum. 
The  ranges  are:  800  to  400  WM,  400  to  305,  305  to  255,  255  to  225  and 
225  to  205.  The  five  adjustments  are:  position  of  collimating  lens, 
angle  at  which  the  prism  is  set,  the  angular  position  of  the  arm  carrying 
the  plate-holder,  the  position  of  the  objective  lens,  and  the  angle  which 
the  plane  of  the  plate-holder  makes  with  the  axis  of  the  plate-holder 
arm.  The  data  furnished  by  the  makers  for  the  various  adjustments 
were  corrected  for  this  particular  instrument  and  plotted  in  such  a  way 
as  to  show  the  relation  between  each  variable  and  the  corresponding 
range.  It  was  found  that  practically  linear  relations  existed,  so  that  it 
was  possible  to  set  for  any  intermediate  range  desired  by  merely  inter- 
polating between  the  given  settings.  A  split  quartz  prism  was  used. 

PRELIMINARY  STUDY. 

A  visual  study  of  a  great  number  of  substances  was  made  in  order  to 
find  out  what  parts  of  the  ultraviolet  spectrum  were  most  capable  of 
exciting  fluorescence,  and  also  what  substances  respond  best  to  such 
excitation,  and  were  therefore  suitable  for  further  study.  The  Fuess 
spectrograph  was  mounted  in  such  a  way  as  to  make  the  plane  of  the 
plate-holder  horizontal.  The  substance  was  spread  out  on  a  piece  of 
glass  or  stiff  paper  and  held  in  the  plane  of  the  plate-holder.  The  follow- 
ing substances  were  examined  in  this  way,  a  record  being  made  in  each 
case  of  the  amount  and  position  of  the  fluorescence  excited  by  the  ultra- 
violet only  (since  the  dispersion  in  this  region  was  good  whereas  the 
visible  part  was  very  narrow).  The  uranyl  compounds  exhibited  the 
strongest  fluorescence.  They  are  given  in  the  order  of  relative  intensity, 
the  first  being  the  brightest.1 

Rubidium  uranyl  nitrate,  Lead  uranyl  acetate, 

Rubidium  uranyl  sulphate,  Ammonium  uranyl  nitrate, 

Potassium  uranyl  sulphate,  Mercury  uranyl  acetate, 

Potassium  uranyl  nitrate,  Calcium  uranyl  acetate, 

Potassium  uranyl  chloride,  Strontium  uranyl  acetate, 

1  The  following  uranyl  compounds  were  found  to  fluoresce  most  strongly  under  x-ray 
excitation:  Rubidium  uranyl  nitrate,  rubidium  uranyl  sulphate,  cesium  uranyl  chloride  and 
lithium  uranyl  acetate. 


VOL.  XX. 
No.  6. 


ULTRAVIOLET   SPECTRUM. 


555 


Uranyl  acetate, 

Sodium  copper  uranyl  acetate, 

Silver  uranyl  acetate, 

Uranyl  tellurate, 

Thanous  uranyl  sulphate. 


Ammonium  potassium  uranyl  chloride, 

Cesium  uranyl  chloride, 

Lithium  uranyl  acetate, 

Cadmium  uranyl  acetate, 

Barium  uranyl  acetate, 

Other  substances  responding  well  to  ultraviolet  excitation  were: 

Anthracene,          If  variable  but  continuous  excitation  between  550  and 

Phenolphthalein,  j  }     200  m/*. 

Calcium  tungstate,  j  ["excitation   between   550  and   350  mju  and 

Phosphorescent  willemite,  I        between  325  and  225  mju  approximately. 

Fluorescein,  Last  two  substances  dissolved  in  water 

Eosin,  J  I     or  alcohol. 

The  following  substances  fluoresced  faintly  by  ultraviolet  excitation: 

CaC2O4,  Cadmium  phosphate, 

Phosphorescent  calcite. 

Zinc  silicate,  Sodium  uranyl  cobalt  acetate. 

Zinc  sulphate,  Sodium  molydate. 

The   following   substances   were   practically   unaffected    by   ultraviolet 
excitation : 

Cesium  chloride, 

Didymium  chloride, 
Lead  chloride, 

Naphthol  yellow, 

Potassium  iodide, 

Rubidium  chloride, 


Barium  chloride, 
Barium  sulphate, 
Berylium  chloride, 
Calcium  fluospar, 
Calcium  sulphate, 
Cadmium  iodide, 
and  the  oxides : 

A12O3,  CaO, 
BaO,  CeO2; 
Bi2O3  CeO, 


Sodium  chloride, 
Sodium  silicate, 

Telluric  acid, 
Thallun  sulphate, 
Tungstic  acid, 
Vanadium  chloride, 


Cr2O3,     PbO,      NiO,       SiO,       UO3, 
CuO,       MgO,     Ni2O2,     SnO2,     ZnO. 
FeO,        MnO,     Sb2O3,     TeO2, 
Three  general  types  of  excitation  were  observed.     First,  a  broad  con- 
tinuous region  of  excitation,  somewhat  variable  in  intensity  and  becoming 
gradually  weaker  further  out  in  the  ultraviolet.     Second,  strong  in  the 
violet  and   near   ultraviolet  to  about  350  mju  where  the   fluorescence 
seems  to  dissappear  over  about  25  m/*  then  to  reappear  over  a  region 
about  100  m/x  long  with  a  maximum  at  about  275  m/z.     Third,  strong  in 
the  violet  and  near  ultraviolet  to  about  350  m/x  where  the  intensity  drops 
very  rapidly  to  practically  zero  in  some  cases  or  to  a  relatively  small 
value   beyond   which   point   the   intensity   gradually   fades  away.     No 
fluorescence  was  observed  beyond  200  m/j,.     Anthracene  is  a  good  example 
of  the  first  type,  calcium  tungstate  and  fluorescein  are  good  examples 
of  the  second  type,  and  the  uranyl  compounds  illustrate  the  third  type. 


556  LELAND   JAYNES  BOARDMAN. 

Photographs  were  obtained  of  the  fluorescent  light  emitted  from  nearly 
all  of  the  substances  listed  above  which  show  any  appreciable  effect. 
The  means  of  mounting  the  material  is  described  in  the  following  para- 
graph. It  was  very  difficult  to  secure  good  photographs  in  some  cases, 
particularly  with  the  liquid  solutions  of  fluorescein  and  eosin.  The 
Fuess  spectrograph  was  used  and  a  camera  lens  of  7  inches  focal  length. 
Exposures  ranging  from  one  minute  to  thirty  minutes  were  necessary. 

METHOD  OF  MOUNTING  THE  FLUORESCENT  SUBSTANCE. 
It  was  necessary  to  have  the  fluorescent  material  offer  a  smooth 
surface  to  the  exciting  light  in  order  to  obtain  a  good  record  on  the 
photographic  plate,  to  which  end  the  following  simple  method  was  used. 
A  strip  of  varnish  or  glue  about  two  centimeters  wide  was  made  across 
the  whole  width  of  the  plate,  and  the  powdered  substance  was  sprinkled 
over  this  with  sufficient  depth  to  cover  it  completely.  Another  glass 
plate  was  then  used  to  press  upon  on  rub  this  surface  till  it  was  made  as 
smooth  as  possible.  Care  was  taken  not  to  leave  any  part  of  the  surface 
in  a  matte  white  condition  due  to  rubbing,  as  such  a  part  may  appear 
on  the  photograph  to  be  different  from  its  surroundings.  In  case  of 
some  of  the  uranyl  salts  the  natural  crystals  are  very  hard  to  reduce  to 
fine  enough  granulations  to  make  a  smooth  surface  possible  in  this  way. 
Some  of  the  photographs  show  this.  In  case  of  liquids  or  solutions  a 
strip  of  quartz  was  used,  and  it  was  mounted  in  such  a  way  as  to  cover 
the  portion  of  liquid  to  be  exposed. 

FURTHER  STUDY  OF  THE  URANYL  COMPOUNDS. 

It  was  mentioned  above  that  the  uranyl  compounds  were  excited  to 
fluorescence  by  wave-lengths  of  light  lying  between  550  m/*  and  350  m/x. 
(Excitation  by  shorter  wave-lengths  than  this  was  very  feeble,  too  faint 
indeed  to  be  photographed.)  In  the  most  intense  part  of  the  excitation, 
as  photographed  by  the  Fuess  spectrograph,  there  appears  to  be  a  short 
region  in  which  the  excitation  is  variable,  giving  what  might  be  called 
bands,  and  this  region  is  the  same  as  that  in  which  absorption  bands  for 
these  same  materials  are  found.  Now  fluorescence  is  undoubtedly  due 
primarily  to  absorption,  though  it  cannot  be  assumed  that  greater 
absorption  will  produce  proportionately  greater  fluorescence.  It  seems 
reasonable  nevertheless  to  expect  that  there  may  be  some  variation  in 
the  excitation  where  there  is  variable  absorption.  If  it  is  true  that  the 
variation  in  the  intensity  of  the  fluorescence  is  due  to  the  changing 
absorption  of  the  dispersed  exciting  light,  this  method  might  well  be  used 
in  detecting  and  studying  the  absorption  of  materials,  for  if  light  of  a 


NoL6XX>]  ULTRAVIOLET  SPECTRUM.  557 

particular  wave-length  is  absorbed  and  this  excites  fluorescence  which 
emanates  from  the  same,  or  neighboring,  spot,  it  would  be  very  easy 
to  observe  this  photographically  in  case  there  is  good  dispersion  of  the 
exciting  light.  The  work  that  follows  is  an  attempt  first  to  test  the 
validity  of  the  assumption  by  seeing  if  fluorescence  bands  do  occur  where 
absorption  bands  are  known  to  exist,  and,  if  the  results  confirm  the 
assumption,  to  locate  the  position  of  as  many  absorption  bands  as  this 
method  is  capable  of  giving,  and  thereby  to  test  the  laws  which  have 
been  found  to  govern  the  arrangement  of  the  bands  previously  observed. 
The  uranyl  salts  are  particularly  good  for  this  work  because  they  give 
many  narrow  bands,  both  in  the  fluorescence  region  of  the  spectrum  and 
in  the  absorption  region. 

THE  FOLLOWING  ARE  THE  COMPOUNDS  TESTED: 

1.  Barium  uranyl  acetate,  7.  Cesium  uranyl  chloride, 

2.  Lithium  uranyl  acetate,  8.  Potassium  uranyl  chloride, 

3.  Mercury  uranyl  acetate,  9.  Potassium  uranyl  nitrate, 

4.  Strontium  uranyl  acetate,  10.  Rubidium  uranyl  nitrate, 

5.  Uranyl  acetate,  1 1.  Cesium  uranyl  sulphate, 

6.  Sodium  copper  uranyl  acetate,  12.  Rubidium  uranyl  sulphate. 
Nichols  and  Howes1  in  their  recent  treatise  entitled  "Fluorescence  of 

the  Uranyl  Salts"  give  a  summary  of  results  showing  the  distribution 
and  character  of  the  fluorescence  spectrum  and  the  absorption  spectrum 
of  many  uranyl  compounds.  It  is  shown  that  the  spectrum  of  the 
fluorescent  light  consists  of  bands  which  naturally  form  eight  groups  of 
five  members  each,  approximately,  ranging  from  640  m/z  to  490  m/*, 
or  thereabouts.  The  absorption  spectrum  consists  also  of  bands  having 
about  the  same  arrangement,  but  ranging  from  490  my  to  380  mju,  appar- 
ently a  continuation  of  the  fluorescence  spectrum.  The  frequency  inter- 
vals (reciprocal  wave-length  intervals)  between  homologous  bands  of 
each  group  are  practically  the  same  throughout  the  spectrum  of  either, 
the  interval  being  about  86  in  the  fluorescence  spectrum  and  about  70 
in  the  absorption  spectrum.  The  last  member  of  the  fluorescence  series 
is  usually  coincident  with  or  at  a  distance  from  the  first  member  of  the 
absorption  series  of  the  homologous  band  of  86  or  70  frequency  units. 
Considering  all  of  the  series  of  the  various  homologous  bands  there  is  an 
overlapping  of  the  fluorescence  and  absorption  spectra  of  about  three 
groups,  called  the  "reversing  region"  because  here  there  are  coincidences 
of  fluorescence  and  absorption  bands. 

In  this  work  a  glass-bulb  nitrogen-filled  tungsten  lamp,  running  at  6 
amperes,  was  used  as  a  source  of  ultraviolet  light.     A  quartz  mercury 

1  Nichols  and  Howes,  Carnegie  Inst.  Wash.  Pub.,  No.  298,  1919. 


558 


LELAND  JAYNES  BOARDMAN. 


[SECOND 
[SERIES. 


lamp  was  used1  for  calibration  purposes,  the  calibration  spectrum  being 
photographed  alongside  of  the  other  spectrum  by  exposing  an  adjacent 
portion  of  the  slit  of  the  spectrograph,  both  exposures  taking  place  at  the 
same  time. 

The  intensity  of  blackening  of  the  plates  was  measured  by  means  of  a 
device  set  up  by  J.  O.  Perrine  in  connection  with  his  work2  on  "  A  Spectro- 

graphic  Study  of  Ultraviolet 
Fluorescence  Excited  by  X- 
rays."  The  apparatus  makes  use 
of  a  photo-electric  cell,  C  in  Fig. 
2,  and  a  sensitive  galvanometer 
G.  The  cell,  which  was  selected 
after  trial  of  several  types,  was 
made  by  Kunz.3  A  Leeds  and 
Northrup  type  C  galvanometer 
was  used  about  6  meters  from 


Fig.  2. 


the  scale  near  the  comparator  and  cell.  The  comparator  carried  the 
photographic  plate  P  just  under  a  slit  2  mm.  by  .25  mm.,  through 
which  a  strong  beam  of  light  from  an  incandescent  lamp  L  was  passed. 
The  lamp  had  one  filament  carrying  a  current  of  about  6  amperes  from  a 
storage  battery.  The  current  could  be  adjusted  to  meet  the  needs  of  the 
plate.  £  is  a  constant  potential  dry  battery  of  about  80  volts.  Further 
description  of  the  apparatus  is  given  in  the  paper  just  cited. 

Much  of  the  success  of  the  present  work  is  due  to  this  apparatus. 
The  instrument,  which  is  highly  sensitive  to  any  variation  in  the  density 
of  the  photographic  image,  has  many  advantages  over  other  methods 
such  as  those  depending  on  the  eye,  but  faulty  places  in  the  photograph 
must  be  carefully  avoided  or  eliminated  by  comparison  with  other  photo- 
graphs. 

METHOD  OF  PLOTTING. 

Curves  were  first  made  from  the  galvanometer  deflections  and  the 
positions  on  the  comparator.  The  intensities  of  the  light  transmitted 
by  the  negative  were  plotted  as  ordinates  and  the  comparator  readings 
as  abscissae,  these  plots  being  made  while  the  measurements  were  being 
made,  i.e.,  plotting  rather  than  recording  the  numbers.  The  intensities 
are  merely  relative,  so  that  a  convenient  arbitrary  scale  was  chosen  to 
represent  them.  The  positions  of  the  mercury  lines  were  located  on  the 

1  The  well-known,  yellowish  green  fluorescence  of  these  substances  is  of  a  color  to  which 
most  photographic  plates  do  not  respond  well.     The  most  satisfactory  of  the  numerous 
plates  tested  was  found  to  be  the  polychrome  plate  made  by  the  Eastman  Kodak  Company. 

2  J.  O.  Perrine;   Thesis  in  M.S.  in  Cornell  University  Library. 

3  Kunz  and  Stebbins,  PHYSICAL  REVIEW,  7,  p.  282. 


VOL.  XX.1 
No.  6. 


ULTRAVIOLET   SPECTRUM. 


559 


plot  by  observing  the  comparator  reading  for  the  smallest  deflection  of 
the  galvanometer;  thus  the  densest  part  of  the  line  was  taken  as  the 
proper  position  of  the  line.  A  setting  could  be  made  to  the  nearest 
tenth  of  a  millimeter.  Five  to  seven  mercury  lines  were  thus  located  on 
each  plot.  Knowing  their  wave-lengths  to  four  significant  figures  their 
reciprocals  were  plotted  (on  another  sheet)  as  ordinates  against  their 
recorded  positions  on  the  plot  as  abscissae,  and  thus  a  calibration  plot 
was  obtained,  giving  the  reciprocal  wave-lengths  for  any  comparator 
reading  on  the  first  plot.  Using  this  calibration  plot  the  final  plot  was 
obtained  where  the  intensities  of  the  light  were  plotted  against  the 
reciprocal  wave-lengths.  A  new  calibration  plot  was  used  whenever 
the  mercury  lines  were  found  to  be  spaced  differently  due  to  different 
magnifications  caused  either  by  a  change  in  the  settings  of  the  spectro- 
graph  or  by  a  change  in  the  camera  adjustment.  Final  curves  were  made 
in  this  way  for  each  of  the  twelve  uranyl  compounds. 

In  these  plots  a  millimeter  represents  2.5  frequency  units,1  and  one 
tenth  of  a  millimeter  on  the  photographic  plate.  The  accuracy  of  the 
data  recorded  in  Tables  I.  to  V.  is  such  that  the  results  are  prob- 
ably correct  to  within  three  frequency  units.  An  estimated  "probable 
error"  is  near  one  frequency  unit.  Typical  curves  are  presented,  greatly 
reduced,  in  Figs.  3,  4,  5  and  6. 


LITHIUM  URAf/YL 

ACETATE 


TH 


Fig.  3. 

J  A  frequency  unit  is  such  that  500  mju  corresponds  to  2000  frequency  units,  i.e. 

i 


.000000500  in  meters 


2000  X  io3. 


56o 


LELAND   JAYNES  BOARD  MAN. 


[SECOND 

[SERIES. 


Peaks  in  the  curves  represent  regions  of  greater  fluorescence.  They 
are  undoubtedly  regions  of  greater  absorption,  and  many  of  them  coincide 
with  absorption  bands  of  these  substances  that  have  been  located  by 


LITHIUH    URANYL    ACETATE 


2,J  I  (I,  ,  1 1,  .IT,  Jl      11(1,1  II,  ,1,  ,1111  ,1,1.1 1  M 
'/#?</  '  tM.  l  'jdW  L-.-7to  J  bioo    '  Ijw  '  V^bo1  (  Woi 


RECIPROCAL    VME-LENGTH 


Woo1 


Fig.  4. 

other  methods.  The  data  in  the  tables  are  arranged  in  two  columns 
so  as  to  show  the  agreement  of  the  results  obtained  by  this  method  and 
measurements  made  by  other  methods.  The  first  column  shows  the 


CESIUM   URANYL   CHLORIDE 


s^ 
t 

1  III 

2  VsW 


III    MM  II    I   Hill  111!  I  HUM    Ml  I   I  I  II  II  111!  II 1 1 1 II 1  Illllll 

1  '/^'  '  *M  '  '^/'oo1  '  ^M  '  'jjto1  '  'f^W  '  'fsbo1  '  ]sAtf  '  'f? 
RECIPROCAL    WAVE-LENGTH 


Fig.  5. 

former,  the  second  column  the  latter  as  published  by  Nichols  and  Howes. 
The  photo-electric  cell  is  so  sensitive  as  to  detect  bands  that  are  not 
apparent  to  the  unaided  eye.  Data  for  these  fainter  bands  seem  to  check 


VOL.  XX. 
No.  6. 


ULTRAVIOLET   SPECTRUM. 


equally  well,  therefore  credence  is  given  to  these  also.  Wherever  there 
is  a  marked  difference  in  the  direction  of  the  curve  such  as  to  indicate  a 
partially  resolved  band  and  wherever  the  main  part  of  an  unresolved  band 
appears  there  is  a  short  vertical  line  drawn  through  the  curve,  and  these 
lines  appear  again  at  the  bottom  of  the  plot.  The  bands  have  been 
designated  by  the  same  symbols  used  by  Nichols  and  Howes.  In  cases 
where  bands  could  not  be  identified,  symbols  were  assigned  so  as  to  agree 
as  nearly  as  possible  with  those  of  the  same  class,  e.g.,  the  acetates, 
nitrates,  etc.,  as  determined  by  Nichols  and  Howes. 

EXTENSION  OF  THE  ABSORPTION  REGION. 

Some  of  the  photographs  show  very  distinctly  that  the  absorption 
bands  extend  further  into  the  ultraviolet  region  than  it  has  been  possible 


CESIUM  WANK.  CHLORIDE 


1          '  'ufa1  '  ^M  ' 

RECIPROCAL  WAVE- LENGTH 


Fig.  6. 

to  go  by  the  other  methods.  Cesium  uranyl  chloride  is  particularly 
rich  in  bands  throughout  the  region  covered  by  the  photograph.  It 
has  been  known  that  this  substance  is  more  fully  resolved  at  ordinary 
temperatures  than  most  of  the  other  uranyl  compounds.  In  order  to 
see  if  the  bands  really  extend  as  far  as  there  is  any  fluorescence  excited, 
a  few  long-time  exposures  were  made,  the  range  being  390  rmx  to  310  rn^u. 
A  quartz-bulb  nitrogen-filled  tungsten  lamp  was  used.  An  exposure  of 
two  hours  was  found  to  be  sufficient  to  register  all  of  the  bands  that  could 
be  recorded  by  the  photographic  plate.  Further  exposure  only  made 
the  black  part  of  the  plate  darker  and  made  the  detection  of  the  bands 
by  the  photo-electric  cell  more  difficult.  In  fact  it  was  necessary  to 
have  regard  to  the  time  of  exposure  in  all  cases  in  order  to  obtain  proper 


562 


LELAND   JAYNES  BOARD  MAN. 


[SECOND 

[SERIES. 


TABLE  I. 

Bands  Appearing  in  Two  or  More  Curves  for  Cesium  Uranyl  Chloride. 
Range  550  m/z  to  370  m/*,  approximately.     See  Fig.  5. 


Curve  a, 
i/X. 

Curve  b,           Curve  c, 
i/X.                i/X. 

Curve  on 
Fig.  6. 

B! 

1812 

1810 

D 

1925 

1925 

B*' 

2032 

2035 



d 

2070 

2072 

.... 

^ 

d' 

2086 

2085 

e*' 

2098 

2095 



b 

2113 

2113 

.... 

b3 

2131 

2130 

d 

.... 

2148 

2145 

d2" 

.... 

2162 

2162 

d' 

2210 

2210 

d 

2218 

2218 

e," 

.... 

2245 

2245 

b,' 

2263 

2263 

2265 

d,' 

2298 

2296 

2297 

b2 

2337 

2336 

2337 

d2 

2367 

2365 

2368 

e2" 

2385 

2388 

2388 

bt' 

2405 

2405 

2405 

d2 

2440 

2438 

2440 

a/ 

.... 

2462 

2464 

b.' 

2473 

2475 

2473 

d.' 

2505 

2505 

2503 

d2 

2512 

2512 

2510 

e2" 

2528 

2530 

• 

b/ 

2543 

2543 

.... 

b3 

2557 

2557 

.... 

di" 

2572 

2572 

....  ^.~«-..« 

d2 

2586 

2586 

*" 

2600 

2602 

2602 

c 

.... 

2632 

.... 

2633 

d 

.... 

2650 

.... 

2650 

e 

2657 

2657 

.... 

.... 

a 

2675 

2675 

bi* 

2687 

.... 

2686 

d/' 

2712 

2710 

.... 

d 

2722 

2722 

.... 

2722 

e 

2730 

2728 



sensitiveness  in  measuring  the  plates.     Too  long  exposures  tend  to  fill 
up  the  places  between  the  bands  and  destroy  the  contrast. 

All  of  the  twelve  compounds  were  photographed  for  the  range  390  m/x 
to  310  rmz,  measurements  were  made,  and  the  data  plotted  in  the  same 
manner  as  in  the  case  of  the  first  range.  Since  the  first  range  extended 


VOL.  XX.l 
No.  6. 


ULTRAVIOLET  SPECTRUM. 


563 


from  about  550  mju  to  370  m/z,  there  was  an  overlapping  of  about  20  m/x. 
This  repetition  aided  in  establishing  the  reality  of  the  bands.  Only  for 
cesium  uranyl  chloride  were  there  independent  measurements  made  with 
the  photo-electric  cell  from  different  photographs  over  the  first  range. 
These  are  plotted  on  the  same  sheet  (Fig.  5).  There  is  also  a  curve  to 
show  the  effect  of  placing  a  screen  between  the  substance  and  the  plate 

TABLE  II. 


Barium  Uranyl  Acetate. 

Lithium  Uranyl  Acetate. 

Uranyl  Acetate. 

B.  Values 
of 
i/X. 

N.  &H. 

Values  of  i/X, 
p.  161,  167. 

B.  Values 
of 

N.  &H. 
Values  of  i/X, 
p.  158,  164. 

B.  Values 
of 

i/X. 

N.  &H. 
Values  of  i/X, 
p.  149. 

1805  I 

1800  A 

1788  E! 

1791  E! 

1830  D 

1828  D 

1827  C 

1825  C 

1803  F 

1802  F 

1862  H 

1852  F 

1852  F 

1820  G 

1817  G 

1888  I 

1870 

1860  B 

1857  B 

1925  E 

1923  E 

1924  D 

1913  H 

1912  H 

1943  G 

1942  G 

1938  F 

1936  F 

1965  E 

1965  E 

1975  I 

19801 

1988  G 

1989  G 

2018  F 

2017  F 

2005  D 

2005  D 

2028  B 

2029  B 

2032  H 

2052  h 

2039  C' 

2039  C' 

2070  C 

2068  h' 

2053  F! 

2056  F! 

2085  D 

2086  D 

2125  h 

2124  h 

2075  G 

2073  G 

2100  F 

2101  F 

2138  h' 

2088  H 

2125  G' 

2152  c' 

2100  e' 

2155  c 

2168  c 

2120  P 

2210  g' 

2185  e 

2185  e 

2150  d 

2245  e' 

2219  c' 

2173  e' 

2275  gh 

2276  gh 

2238  c 

2235  c 

2210  i 

2305  c" 

2285  c 

2215  g 

2345  gh 

2338  h 

2223d 

2365 

2350  h' 

2260.P 

2395  e 

2394  e 

2360  c' 

2270k 

2420  gh 

2419  gh 

2373  c 

2373  c 

2281  i 

» 

2450  P 

2415  h' 

2303  c 

2475  g 

2443  c 

2446  c 

2315  e' 

2488  gh 

2487  gh 

2455  f 

2323  e 

2502  c 

2470  e 

2340k 

2520  P 

2488  h' 

2353d 

2530  e" 

2513  c 

2515  c 

2388  f 

2548  g 

2545  h 

2412  k 

2560  gh 

2565  c 

2445  c 

2568  c' 

2586  c 

2585  c 

2465  e 

2578  c 

2603  g 

2490  i 

2600  e" 

2610  e 

2503d 

2615  g 

2618  h 

2518  c 

2626  h' 

2635  c 

2538  e 

2632  gh 

2650  c 

2547  P 

LELAND   JAYNES  BOARD  MAN. 

TABLE  II. — continued. 


[SECOND 
[SERIES. 


Barium  Uranyl  Acetate. 

Lithium  Uranyl  Acetate. 

Uranyl  Acetate. 

B.  Values 
of 

i/X. 

N.  &H. 
Values  of  i/X, 
p.  161,  167. 

B.  Values 
of 

i/X. 

N.  &H. 

Values  of  i/X, 
p.  158,  164. 

B.  Values       N.  &  H. 
of       Values  of  i/X, 
i/X.         p.  149. 

2665  e' 

2663  c 

2557 

2688  g 

2678  e 

2563  i 

2707  c' 

2688  h 

2576  d 

2728  f 

2698  h' 

2585  c 

2738  e' 

2711  c' 

2593  e' 

2748  e 

2724  c 

2602  f 

2757  g 

2743  g 

2607  e' 

2770  gh 

2750  e 

2618  P 

2790  c" 

2778  c 

2633  i 

2805  e' 

2790  c 

2638  g 

2815  e 

2810  g 

2653  c 

2843  gh 

2828  h 

2675  e 

2855  c 

2850  c' 

2680  x 

2867  f  ' 

2889  e 

2690  f  ' 

2877  e' 

2907  h' 

2697  k 

2888  e 

2915  c 

2708  g 

2905  h' 

2925  c 

2718  d 

2922  c' 

2982  c 

2740  f 

2930  c" 

3003 

2748  x 

2943  e' 

2763  k 

2978  gh 

2777  g 

2995  c 

2789  d 

3030  e 

2813  e 

3085  e' 

2825  P 

3122  c' 

2838  k 

3148  f 

2848  g 

2880  e 

2923d 

2948  e 

2973  k 

3028  x 

3057  g 

3075  d 

3118  k 

3128  g 

3143d 

3165  x 

with  the  hope  of  screening  off  some  of  the  visible  light  diffusely  reflected 
from  the  substance.  This  procedure  was  however  not  satisfactory.  One 
purpose  of  the  three  plots  (or  curves)  for  cesium  uranyl  chloride  is  to  show 
how  well  the  bands  check.  The  data  are  given  in  Table  I.  Bands  that 
appear  in  two  or  more  curves  are  given  in  parallel  columns.  It  can  be 
seen  that  the  differences  are  few  in  number  and  are  well  within  the 
experimental  error. 


VOL.  XX. 1 
No.  6. 


ULTRAVIOLET   SPECTRUM. 


565 


DISCUSSION  OF  RESULTS. 

In  Tables  II.  to  V.  comparison  is  made  with  former  data  obtained 
when  the  substance  was  at  the  temperature  of  liquid  air,  —  185°  C. 
This  seems  justifiable  because  of  the  fact  that  some  of  the  compounds 
are  partially  resolved  at  room  temperature,  so  that  the  components, 
which  are  separated  quite  well  by  the  relatively  large  dispersion  of  the 
spectrograph,  show  up  well  when  measured  by  the  photo-electric  cell. 

A  comparison  of  the  results  obtained  by  the  present  method  with 
those  of  other  methods  seems  to  establish  the  fact  that  the  position  of  the 
absorption  bands  can  be  determined  by  the  fluorescence  that  the  absorption 
gives  rise  to,  a  fact  already  established  by  Howe1  in  the  case  of  certain 
phosphorescent  sulphides.  Not  all  absorption  bands  may  have  the 

TABLE  III. 


Potassium  Uranyl  Nitrate. 

Potassium  Uranyl  Chloride. 

Rubidium  Uranyl  Sulphate. 

B.  Values 
of 

i/X. 

N.  &H. 
Values  of  i/X, 
P.  139- 

B.  Values 
of 
i/X. 

N.  &H. 
Values  of  i/X, 
P-  90-93. 

B.  Values 
of 
i/X. 

N.  &H. 

Values  of  i/X, 
p.  174.  178. 

1795  D 

1794  D 

1761 

1810  I 

1812  I 

1823  I 

1824  I 

1787  A! 

1785  A! 

1822  A' 

1860  B 

1862  B 

1815  Ci 

1816  Ci 

1842  C 

1844  C 

1978  E 

1976  E 

1945  Ea' 

1940  Ea' 

1872  F 

1872  F 

2005  J 

2007  J 

1987  C2 

1988  C2 

1907  A' 

1908  A' 

2070  F 

2069  F 

2012  d3 

2014  d3 

1948  E 

1947  E 

2093 

2085  d3 

1957  F 

1955  F 

2127  d 

2155  d3 

2155  d3 

1990  A' 

1992  A' 

2162  f 

2237  e2' 

2012  C 

2011  C 

2188  I' 

2268  c2' 

2264  c2' 

2063  bi 

2066  bi 

2268  d 

2269  d 

2335  c2' 

2333  ca' 

2078 

2337  d 

2375  ea' 

2375  ea' 

2093  ei 

2096  ei 

2372  f 

2369  f 

2390  a 

2392  a 

2133  bi 

2137  bi 

2394  1' 

2397  V 

2456  ai 

2456  ai 

2165  ei 

2425  j 

2468  c2 

2190  g 

2188  g 

2450k 

2477  c2' 

2205  bi 

2206  bi 

2492  j 

2530  a2" 

2533  a2" 

2238  ei 

2522  k 

2548  c2' 

2268  h 

2267  h 

2535  1' 

2595  ai 

2595  ai 

2282  ci 

2563  j 

2613  ca' 

2300  d 

2301  d 

2580  f 

2626  di 

2322  gl 

2322  gl 

2605  1' 

2655  ea' 

2340  h 

2341  h 

2618  d 

2665  ai 

2375  ei 

2375  ei 

2637  j 

2675  c2 

2410  h 

2409  h 

2655  f 

2698  d! 

2420  b, 

2675  1' 

2726  ea' 

2430  c 

2703  j 

2737  ai 

2450  ei 

2450  ei 

2722  f 

2755  ca' 

2482  h 

2745  1' 

2782  d3 

2498  ci 

1  Trans.  Am.  Philos.  Soc.,  LVL,  p.  259  (1917). 


566 


LELAND   JAYNES   BOARD  MAN. 


[SECOND 

[SERIES. 


TABLE  III. — continued. 


Potassium  Uranyl  Nitrate. 

Potassium  Uranyl  Chloride. 

Rubidium  Uranyl  Sulphate. 

B.  Values 

N.  &H. 

B.  Values 

N.  &H. 

B.  Values 

N.  &H. 

of 

Values  of  i/X, 

of 

Values  of  i/X, 

of 

Values  of  i/X, 

i/X. 

P-  139- 

i/X. 

p.  90-93- 

i/X. 

p.  174.  i?8. 

2757  d 

2800  bi' 

2522  ei 

2798  k 

2807  ai 

2550  h 

2813  1' 

2818  c2 

2572  c 

2853 

2835  di 

2585  d 

2883  1' 

2850  d3 

2606  g, 

2898  d 

2876  ai 

2622  h 

2915  j 

2887  c2 

2637  ci 

2928  f 

2898  c2" 

2653  d' 

2953  1' 

2918  d3 

2667  e: 

2983  j 

2939  bi' 

2680  g 

3032  d 

2950  c2 

2705  ci 

3050  j 

2968  c2" 

2715  c 

3075  k 

2998  e2' 

2724  d 

3100  d 

3018  ai 

2738  ei 

3042  di 

2745  gl 

3080  b/ 

2757  hi 

3100  c2' 

2782  ci 

3128  ds 

2803 

3151  a 

2820  g 

2838  bi 

2855  c 

2898  hi 

2915  ci 

2930  c 

2949 

2978  bi 

3000  c 

3040  hi 

power  of  exciting  fluorescence,  and,  if  so,  such  bands  would  not  appear 
on  the  plate.  This  may  explain  why  some  bands  are  missing  by  this 
method.  Most  of  the  known  bands  do  appear  however  and  many  more 
besides.  Where  formerly  the  absorption  spectrum  was  observed  only 
between  490  m/x  and  380  rmz,  approximately,  the  range  is  extended  by  this 
method  in  both  directions,  i.e.,  550  m/*  to  322  mju,  or  through  a  frequency 
range  of  1800  to  3100.  In  the  extension  toward  the  shorter  wave- 
lengths the  bands  readily  fall  into  the  series  already  determined,  a  fact 
which  strengthens  the  belief  that  all  regions  showing  fluorescence  really 
serve  to  locate  absorption  bands. 

In  a  few  instances  there  seemed  to  be  a  new  series  starting  somewhere 
near  the  middle  of  the  complete  absorption  region,  but  more  observations 
are  needed  to  establish  this  if  such  is  the  case.  Series  of  this  sort  are 


VOL.  XX.l 
No.  6. 


ULTRAVIOLET   SPECTRUM. 


567 


indicated  by  letters  in  the  latter  part  of  the  alphabet.  Again,  there  is 
some  indication  that  the  intensity  of  the  members  of  the  series  varies 
as  we  go  through  the  spectrum,  resulting  in  more  than  one  maximum. 
If  this  is  true  it  may  explain  the  apparent  omission  of  a  part  of  the  series 
due  to  the  faintness  of  the  bands,  as  can  be  noted  in  some  cases. 

REVERSING  REGION. 

The  so-called  reversing  region  lies  within  the  seventh,  eighth  and  ninth 
groups  of  the  fluorescent  spectra,  i.e.,  2,000  to  2,200  frequency  units 

TABLE  IV. 


Cesium  Uranyl  Sulphate. 

Strontium  Uranyl  Acetate. 

Sodium 
Copper 
Uranyl 
Acetate. 

Mercury 
Uranyl 
Acetate. 

Rubidium 
Uranyl 
Nitrate. 

B.  Values 
of 
i/X. 

N.  &H. 
Values  of  i/X, 
p.  175,  178. 

B.  Values 
of 
i/X. 

N.  &H. 
Values, 
p.  160,  166. 

1795  E 

1794  E 

1810 

1820  C 

1798  A 

1788  D 

1815  G 

1813  G 

2000  D 

2004  D 

1873  B 

1812  B 

1807  F 

1845  B 

1848  B 

2050  H 

2046  H 

1975  A 

1885  B 

1840  K 

1864  C 

1861  C 

2128  h' 

2000  D 

1980  C 

1852  L 

1903  G 

2200  h' 

2206  h' 

2040  B 

2015  c' 

19101 

1915  I 

1913  I 

2270  h 

2274  h 

2080  C 

2030  c 

1923  K 

1952  D 

1954  D 

2287 

2100  f 

2085  c' 

1960  D 

1990  H 

1993  H 

2302  j 

2128  b 

2150  h 

2045  D 

20181 

2337  h' 

2152  h 

2200  g 

2095  K 

2035  c' 

2036  c' 

23501 

23501 

2205  g 

2218  h 

21201' 

2050  E 

2052  E 

2400  e" 

2400  e" 

2263  fi 

2252  e 

2193  1' 

2063  f      2061  f 

2437  a 

2275  g 

2320  e 

22185 

2080  h     2077  h 

2516  j 

2300  h 

2365  c' 

2270  d 

20871 

20851 

2544  h' 

2340  g 

2405  h' 

2295  h 

2102  c 

2104  c 

2578  a 

2365  h 

2427  h 

2338  d 

2138  g 

2613  h' 

2410  g 

2455  d 

23605 

2147  g' 

2144  g' 

2655  j 

24201 

24931 

2375  f 

2165  a 

2165  a 

2680  e" 

2473  fi 

2514  c 

23901 

2192  e 

2695  h 

2538  f/ 

2532  e 

2402  1' 

2222  g' 

2718  a 

25641 

25631 

2432  h 

2232  a 

2732  b 

2573  h 

2590  f 

2473  1' 

2280  g 

2280  g 

27701 

2590  f 

2602  e 

2505  h 

2290  g' 

2799  b' 

2605  f  i' 

2622  g 

2527  1 

2307  a 

2811  c 

2620  g 

26331 

2550  d 

2320  c' 

2820  e" 

2627  g' 

2660  f 

25705 

2352  g 

2835  h 

2632  i 

2677  ft 

2585  f 

2372  a 

2875  b 

2655  c' 

27031 

2595  1 

2405  e 

2903  h 

2660  f 

2707  h 

2618  d 

2428  g' 

2427  g' 

2928  a 

2675  £/ 

2722  c 

2626  e 

2460  c' 

2945  b 

2680  fi 

2732  f 

2635 

2480  e' 

2965  h' 

2688  g 

2738  d 

2649  x 

2500  g' 

24981 

2975  h 

2703  i 

2755  h' 

2655  f 

2530  c' 

3010  b' 

2713  h 

2770  ci 

2660k 

1  No  letters  assigned. 


568 


LELAND   JAYNES  BOARD  MAN. 


[SECOND 


TABLE  IV. — continued. 


Cesium  Uranyl  Sulphate. 

Strontium  Uranyl  Acetate. 

Sodium 
Copper 
Uranyl 
Acetate. 

Mercury 
Uranyl 
Acetate. 

Rubidium 
Uranyl 
Nitrate. 

B.  Values 
of 

i/X. 

N.  &H. 
Values  of  i/X, 
p.  175.  178. 

B.  Values 
of 

i/X. 

N.  &H. 

Values, 
p.  160,  166. 

2543  e 

25431 

3020  c 

2728  f 

2780  h 

26701 

2550  e' 

3093  c 

2753  fx 

2799  f 

2680  1' 

2568  g' 

25671 

27701 

2823  fi 

2698  e 

25781 

2780  h 

2835  g 

2712  h 

2595  c 

2793  c' 

2850  h 

2730k 

2605  di 

2813  f/ 

2898  h' 

2743 

2615  e 

26131 

2835  g' 

2910  Cl 

2750  1' 

2626  f 

2850  h 

2921  h 

2755  d 

2643  g' 

2863  c' 

2960  fi 

2770  e 

2675  di 

2876 

2978  Cl 

2780  S 

2692  e' 

2903  g' 

3015  f 

2802  k 

2703  g 

2922  h 

3050  ci 

2822  1' 

2726  a 

2934  f 

3170  fi 

2827  d 

2756  e 

2968  g 

2835  e 

2770  g 

3005  f 

2859  x 

27891 

3040  g' 

2865  f 

2820 

3068  c' 

2870  k 

2850  g' 

3097  fi 

2898  d 

2874  c 

3168fi 

2925  h 

2885  di 

2939k 

2906  e' 

2953 

2920  g' 

2965  d 

29281 

2988  S 

2947  c 

3002  x 

2975  e' 

3010k 

2993  g' 

3028  1' 

3001  1 

3045  e 

3026  di 

3075  f 

3052  g 

30891 

30681 

3118  e 

3133  g' 

3139  x 

3168  di 

3150  k 

3173  1' 

approximately.  This  region  is  extended  further  toward  the  long  wave 
lengths  if  credence  is  given  to  the  bands  herein  contained  and  if  these 
bands  are  due  to  absorption,  for,  if  any  point  on  the  plate  containing 
the  fluorescent  material  is  being  excited  to  fluorescence  by  the  absorption 
of  light  of  a  particular  wave-length,  this  absorption  being  due  to  the 
fluorescent  material  itself,  there  is  evidently  a  reversal  wherever  the 
wave-length  of  the  exciting  light  is  equal  to  the  wave-length  of  a  band  of 
the  fluorescence  spectrum.  In  the  tables  there  are  shown  several  bands 
agreeing  well  with  the  bands  of  the  fluorescence  spectra,  i.e.,  as  well  as 


VOL.  XX.1 
No.  6. 


ULTRAVIOLET  SPECTRUM. 


569 


TABLE  V. 

Cesium  Uranyl  Chloride. 


B.  Values 
of 

i/X. 

N.  &  H.  Values 
of  i/X, 
P-  90-93- 

B.  Values 
of 
i/X  con. 

N.  &  H.  Values 
of 

i/X. 

B.  Values 
of 
i/X  con. 

1785  E2' 

2405  b2' 

2405  b2' 

2788  d2' 

1812  Bi 

1810  Bx 

2409  b2 

2410  b2 

2793  d2 

1828  C 

1828  C 

2415  b3 

2416  b3 

2804  e,' 

1845  D! 

1843  D! 

2435  d2' 

2436  d2' 

2810  e2" 

1855  D2' 

1854  D2' 

2440  d2 

2441  d2 

2819  b 

1868  E2" 

1866  E2" 

2455  e2 

2828  b/ 

1906  B3 

2462  a/ 

2839  b3 

1924  D 

1924  D 

2474  b/ 

2476  b2' 

2850  d 

1950  E2" 

1950  E2" 

2489  c 

2857  d27 

1963  A2 

1964  A2 

2505  d2' 

2509  d2' 

2865  d2 

1985  B2 

1985  B2 

2512  d2 

2513*d2 

2874  e2' 

1998  Ci 

1998  Ci 

2528  e2" 

2530  e2" 

2884  e2" 

2032  E2' 

2030  E2' 

2543  b2' 

2895  b2' 

2065  c 

2064  c 

2557  b3 

2911  c 

2070  d' 

2071  d' 

2572  d/' 

2920  d 

2085  d2' 

2086  d2' 

2586  d2 

2585  d2 

2930  d2' 

2098  e2' 

2100  e2' 

2601  e2" 

2940  d2" 

2107  a 

2615  b2' 

2966  b2' 

2113  b 

2114  b 

2625  b3 

2973  b2 

2131  b3 

2132  b3 

2632  c 

2980  b3 

2137  ci' 

2135  c/ 

2645  d2' 

2984  c 

2147  d 

2146  d 

2650  d2 

2990  d 

2162  d2" 

2164  d2" 

2657  e 

3003  d2 

2185  b 

2184  b 

2665  e2" 

2670  e2" 

3010  d2r/ 

2210  d' 

2212  d' 

2675  a 

2674  a 

3020  e2" 

2218  d 

2680  b 

3032  b 

2230  d2 

2229  d2 

2687  b2' 

3043  b2 

2238  e2' 

2239  e2' 

2693  b2 

3055  c 

2245  e2" 

2245  e2" 

2702  c 

•3062  d 

2263  b/ 

2263  b2' 

2712  d 

3077  d2" 

2297  d2' 

2296  d2' 

2722  d2 

3092  e2" 

2310  e 

2310  e 

2730  e 

3102  b 

2315  e2 

2314  e2 

2736  e2' 

3137  d2' 

2337  b2 

2740  e2" 

3155  e2' 

2368  d2 

2369  d2 

2748  a 

2388  e2" 

2389  e2" 

2750  b 

the  precision  of  the  work  warrants.  These  therefore  indicate  more 
reversals  than  have  been  heretofore  obtained,  and  that  the  number  of 
reversals  in  any  one  series  is  not  limited  to  one,  but  may  be  as  great  as 
two  or  three. 

It  is  rather  curious  that  most  of  the  new  reversals  are  on  the  long 
wave-length  side  of  the  "reversing  region"  as  given  by  Nichols  and 


570 


LELAND  JAYNES  BO  A  RDM  AN. 


[SECOND 
[SERIES. 


Howes.  In  the  cases  of  potassium  uranyl  chloride  and  rubidium  uranyl 
sulphate  none  of  the  reversals  by  this  method  has  been  observed  by  other 
methods.  This  is  true  with  cesium  uranyl  chloride,  excepting  the  series 
E2".  The  methods  give  results  that  agree  in  series  F  of  cesium  uranyl 
sulphate.  It  must  be  admitted  however  that  more  data  are  needed  in 
order  to  confirm  or  disprove  the  existence  of  the  new  reverasls.  In  cases 
where  several  photographs  were  made  for  the  same  substance  there  is  a 
close  agreement  between  the  independent  measurements,  so  that  one  is 
convinced  that  the  method  is  capable  of  giving  results  quite  comparable 
with  those  obtained  by  other  methods. 

The  following  table  (VI.)  shows  the  reversals  of  the  bands  in  the 
various  substances  studied.  The  wave  numbers  in  the  first  column  are 
from  Tables  II.  to  V.,  and  those  to  the  right  are  from  the  tables  given 
by  Nichols  and  Howes  on  the  pages  indicated.  Values  in  parentheses 
indicate  that  the  corresponding  band  of  the  fluorescence  spectrum  is 
missing,  or  that  it  is  not  recorded  by  them.  References  are  also  missing 
for  mercury  uranyl  acetate,  sodium  copper  uranyl  acetate,  and  rubidium 
uranyl  nitrate,  and  they  are  therefore  not  included  in  the  table. 

TABLE  VI. 

Reversals  of  the  Uranyl  Bands. 


Reversals  by  Present  Method. 

Barium  uranyl  acetate 
Series 

D       reverses  at    1830   and   2085 

F  "         "    2018      "      2100 

Potassium  uranyl  chloride 
Series 

E  "         "     1925 

G  "         "     1943 

(H)  "         "  (1862)     "     (2032) 

(I)  "         "(1805)    "     (1888)  and  (1975), 

Lithium  uranyl  acetate 

F       reverses  at  1852  and  1938 

C  "         "  1827 

D  "         "  2005    "     (1924) 

Strontium  uranyl  acetate 

D       reverses  at  2000 

H  "         "  2050 

Uranyl  acetate 

E       reverses  at  1788 

F'  "         "  1803 

G  "         "  1820,  1988  and  2075 

H  "         "  1913  (2088) 

B  "         "  1860,  2028 

E  "         "   1965 

C'  "         "  2039 

F'  "         "  2053 


Reversals  Observed  by  Nichols  and  Howes. 
(Pages  161,  167) 

E  reverses  at  2009 
(Pages  88-101) 


(Pages  158,  164) 

F'  at  2105  reverses  approximately  with 
Pat  2 109. 

(Pages  160,  166) 


(Page  149) 


VOL.  XX.l 
No.  6. 


ULTRAVIOLET   SPECTRUM. 


571 


TABLE  VI. — continued. 


Cesium  uranyl  chloride 

E2" 

reverses  at  (1785),  1868,  1950,  2032 

B 

"     1812 

C' 

"     1828 

D' 

"     1845 

D,' 

"     1855 

D 

"     1924 

A2 

"     1963 

B2 

"     1985 

Ci 

"     1998 

Ai 

reverses  at  1787 

Ci 

"   1815 

E2' 

"   1943 

C2 

"   1987 

Potassium  uranyl  nitrate 

D 

reverses  at  1794 

I 

"   1824 

B 

"   1862 

E 

"   1976 

J 

"  2007 

F 

"  2069 

Cesium  uranyl  sulphate 

E 

reverses  at  1795 

G 

"   1815,  (1903) 

B 

"   1845 

C 

"   1864 

I 

"   1915 

D 

"   1952 

H 

"   1990 

F 

"    2063 

Rubidium  uranyl  sulphate 

I 

reverses  at    1810 

A' 

"   (1822),  1907,  1990 

C 

"     1842,    2012 

F 

"     1872,    1957 

E 

"     1948 

(Pages  88-101) 
B  reverses  at  1974 
C  "  "  1993 
D  "  "  2005 
E  "  "  2026 
A  "  "  2037 
E2'  "  "  2030 


E2' 


2034 


B  reverses  at  1969 
C  "  "  1984 
D  "  "  2004 
fi  *V  "  2022 
A2  "  "  2039 
(Page  139)  ' 


(Pages  173,  178) 
F  reverses  at  2061 


(Pages  174,  178) 
Ei  reverses  at  2028 
F          "         "  2038 
Gi        "         "  2045 

G          "         "  2049 

SUMMARY. 

Fluorescence  is  excited  by  wave-lengths  of  light  between  550  m/i  and 
200  m/z,  approximately.  The  intensity  and  range  of  excitation  depends 
upon  the  substance. 

There  are  three  types  of  excitation  observed : 

1.  Continuous,  but  variable  in  intensity,  between  550  and  200  m/z. 

2.  Continuous,  but  variable  in  intensity,  between  550  and  350  m^. 

3.  Discontinuous,  exhibiting  a  gap  between  350  and  325  m/i,  otherwise 

like  type  I. 

The  range  of  the  absorption  spectra  of  twelve  uranyl  salts  is  extended 
to  550  mn  and  to  320  m/z  by  the  method  herein  discussed,  a  method 


572  LELAND   JAYNES  BO  A  RDM  AN.  [iS?E? 

which  makes  use  of  the  fluorescence  excited  by  dispersed  ultraviolet 
light,  observing  that  wherever  greater  absorption  takes  place  greater 
fluorescence  results  therefrom. 

It  is  desirable  to  continue  the  work  on  the  uranyl  salts  by  this  method, 
especially  in  the  reversing  region,  because  it  is  here  that  information 
can  doubtless  be  obtained  about  the  real  mechanism  of  fluorescence. 

The  gap  at  350  to  325  m/z  in  case  of  a  few  substances  noted  is  rather 
curious.  No  explanation  is  given,  but  further  study  of  this  type  of 
excitation  is  desirable.  It  was  observed  that  one  of  the  uranyl  com- 
pounds, namely  sodium  uranyl  cobalt  acetate,  appeared  to  the  eye  to 
give  this  type  of  excitation,  but  it  was  not  studied  photographically 
because  of  the  relatively  weak  fluorescence  produced. 

The  writer  wishes  to  express  his  gratitude  to  Professor  Ernest  Merritt 
under  whose  guidance  this  work  has  been  performed. 

PHYSICAL  LABORATORY, 
CORNELL  UNIVERSITY. 


5077 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


